#include<stdio.h>
void change(int *a,int *b)
{
    int temp;
    temp=*a;
    *a=*b;
    *b=temp;
}
int main()
{
    int a=10;
    int b=20;
    printf("前:a=%d,b=%d\n",a,b);
    change(&a,&b);
    printf("后:a=%d,b=%d\n",a,b);
}